Production positioning system

ABSTRACT

A positioning method for a production system for positioning the location of a positioning head (2 12, 27) in relation to a work object, comprising a positioning body (1, 11), e.g. a robot or a machine tool, a positioning control unit (3) for the positioning body (1, 11) and a control data system (4) for the positioning control unit (3), wherein the control data system (4) communicates with a three-dimensional localisation measuring system (6) comprising at least one recording device (7) which determines and adjusts the location of the positioning head (2, 12, 27) in space and a positioning device for a production system for positioning the location of a positioning head (2, 12, 27) in relation to a work object, comprising a positioning body (1, 11), e.g. a robot or a machine tool, a positioning control unit (3) for the positioning body (1, 11) and a control data system (4) for the positioning control unit (3), wherein the control data system (4) is arranged to communicate with a three-dimensional localisation measuring system (6) comprising at least one recording device (7) for determining and adjusting the location of the positioning head (2, 12, 27) in space.

TECHNICAL FIELD

The present invention relates to controlling production systems such asindustrial robot applications for the workshop industry, for measuringsystems, for surgical applications, etc. The invention also relates tocontrolling applications for machine tools.

More particularly the invention relates to electro-optical measuringsystems in combination with control of said applications.

BACKGROUND ART

Most of the individual components used for the present positioningmethod and positioning device are already known but have not previouslybeen combined in the present manner.

Previously known positioning systems for industrial robots, forinstance, are controlled in a similar manner to numerically controlledmachine tools, i.e. a positioning control unit receives input datavalues from a control data system, whereupon the control unit transmitscontrol data concerning positions in three dimensions, speed of rotationand other motion to the positioning member with its positioning head.

This control occurs completely independently of the position of a workobject. All movements and positions of the positioning head presuppose awork object with a specific location and with specific dimensions. Thesecuring of the work piece and the location of all parts of the workpiece thus determine the tolerances achieved for the work operation.Adjustment must be made, for instance, for temperature variations, wearin bearings and other factors having a negative influence on thelocation initially determined between the work object and thepositioning head. This is a considerable drawback in existing systems.

OBJECT OF THE INVENTION

The object of the invention is to control robots or other systems suchas those mentioned above, using a device and a method that does not havethe described drawbacks of existing systems, for various tasks withelectro-optical systems such as 3D-vision systems, laser followersystems, interferometer systems, etc. A particular feature of thepresent invention is the control of a positioning head in relation to awork object.

The control is achieved by means of a fundamental localisation measuringsystem as a part of the invention, which enables determination of thespace coordinates for target points with extremely high accuracy andwhich can calculate the spatial location of other mechanical elementsconnected to a rigid body provided with target points.

A control data system in the present invention can determinedisplacements between the actual position of a positioning head and itsset location in order to update the control program and can also controlthe positioning head as required in order to compensate for suchdisplacements.

Recording devices are arranged in order to determine the relativelocation between the positioning head and the work object, whichrecording devices may, for example, use photogrammetry and/or 3-D-visiontechnology in order to calibrate the location of the positioning head.

Another object of the invention is to control a robot of the typedefined in Swedish patent application No. 8502327-3 in accordance withthe method, and using the device revealed by the present invention.

SUMMARY OF THE INVENTION

The invention shows a method and a device for a production system forpositioning the location of a positioning head in relation to a workobject, comprising a positioning body, e.g. a robot or a machine tool, apositioning control unit for the positioning body, and a control datasystem for the positioning control unit, wherein the control data systemcommunicates with a three-dimensional localisation measuring systemcomprising at least one recording device which determines and adjuststhe location of the positioning head in space.

The invention also shows a method and a device according to the abovewherein the recording device can also simultaneously record anddetermine the location of the positioning head and the location of thework object in space.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings in which

FIG. 1 shows a production positioning system according to the presentinvention,

FIG. 2 shows a production positioning system according to the presentinvention intended for a robot,

FIG. 3 shows a perspective view of a robot according to FIG. 2.

DESCRIPTION OF THE INVENTION

The positioning device comprises a positioning body 1 provided with apositioning head 2, said body and head being arranged to be controlledrepeatedly by a positioning control unit 3 to an optional location in agiven work volume. The positioning device also comprises a control datasystem 4 for communication with the positioning control unit 3. Two-waycommunication occurs between the control data system 4 and thepositioning control unit 3, as indicated in FIG. 1 by two-directionalcommunication arrows.

The positioning body 1, positioning head 2, positioning control unit 3and control data system 4 constitute in known manner a conventional NCmachine or a conventional industrial robot.

The positioning device according to the embodiment of the inventionshown in FIG. 1 is also provided with a CAD system 5 which can directlysupply the control data system 4 with control data. The control datasystem 4 can receive control data as input data in numerous other waysthan through the CAD system shown here.

A three-dimensional localisation measuring system is connected to thecontrol data system 4 for two-way communication, by which is meant thatthe system is capable of recording measured points in the recordingdevice and then, by processing the data recorded, to determine the spacecoordinates of the points. The localisation measuring system is used forits ability to record and determine the position of a measured point inspace. The measuring system requires target devices placed on the workobject and/or on or at a fixed point in the vicinity of the positioninghead 2, that can be accurately measured. The target devices may be ofany type whatsoever where the position can be determined by anelectro-optical device. The target devices may, for example, bereflecting target surfaces, light diodes, prisms, tool apertures,spheres, etc. With the aid of these target devices the localisationmeasuring system can record and calculate space coordinates for thelocation of the target devices in a given work volume in order to beable to transmit this information on to the control data system 4 whichin turn communicates with the positioning control unit 3 for control ofthe positioning head 2.

One or more recording devices 7 is/are connected to the localisationmeasuring system 6 for positional determination of the space coordinatesof the target devices. These recording devices 7 may consist ofelectro-optical devices which are directly connected to the localisationmeasuring system for further calculation of the space coordinates. Therecording devices 7 thus record the location of the target devices atcertain predetermined time intervals to enable said further calculation.The localisation measuring system 6 or the control data system 4 canalso calculate the difference between two consecutive recording andpositional determination occasions and, with the aid of the positioningcontrol unit 3, adjust the positioning head 2 for this difference. Thismeans that any alteration in the location of the work object, e.g. dueto temperature, in relation to the location of the positioning head 2 isadjusted by the positioning device in real time, i.e. while a workoperation is in progress.

In the embodiment shown in FIG. 1 an object identifier 8 is connected tothe positioning control unit 3 in order to directly trace the surface ofthe work object before the positioning head 2 arrives at this position,to adjust the positioning head 2 directly via the positioning controlunit 3 for any deviations in the location of the surface. The objectidentifier 8 is thus a supplementary adjustment means in the system.

The localisation measuring system 6 is thus an electro-optical systemfor determining the relative location of the positioning head 2 inrelation to a work piece or some other reference coordinate system.

The positioning device also constitutes a control system which providesthe positioning body and its positioning head with adjustments for itspath and/or which directly calculates updated positions based onrequested locations and observed locations.

The positioning method according to the present invention can bedescribed in the following steps.

Step 1: Target devices are secured to a work object and/or a componentwhich retains the work object in a fixed relative spatial location.

Step 2: The space coordinates from these target devices are determinedby the use of some form of recording device. This device may consist ofthe same electro-optical device as described above or some othermeasuring device such as a coordinate measuring machine, theodolite,laser tracer, etc.

Step 3: The target devices are secured to the bodies to be positionedand/or to adapters having a fixed relationship to the body to bepositioned. For a drilling operation, for instance, the target devicescan be secured on the drill spindle or on adapters having a fixedrelationship to the spindle holder.

Step 4: The relationship between the target devices on the bodies, e.g.the end of a drill spindle, or an adapter to be positioned is determinedeither by an external measuring device or by using the electro-opticalsystem described above with the aid of special routines

Step 5: An electro-optical device, e.g. a 3D vision system as in thepresent implementation, uses the target devices secured in accordancewith steps 1 and 3 to determine the spatial location of the positioninghead 2 in some coordinate system. Other devices are, however, possible.This coordinate system may be a coordinate system for a work cell, acoordinate system to a fixture, a coordinate system to an object, i.e.the coordinate system to the work object in relation to which thepositioning system is to be placed, or some other coordinate system.

Step 6:

Procedure 1: Step 5 is performed in a plurality of locations, andadjustments in the form of a mean difference are calculated betweenlocations of the positioning head 2, i.e. the locations the robot"thinks" it is in, and the measured locations. The adjustments are usedto control the positioning head 2 in the work volume defined throughthese locations but not limited by them to adjust the spatial locations.For this purpose the robot and/or machine control program can be updatedand the adjustment values can be sent to the robot and/or machine.

Procedure 2: The positioning head is controlled to its exact location byusing a feedback loop in which an electro-optical system as describedabove effects measurements in real time in order to control thepositioning head 2.

A recording, a positional determination and an adjustment are thusperformed, i.e. a coordinate determination followed by an adjustment ofthe location of the positioning head 2 and of the work object in space.

The localisation measuring system 6 described above may be amulti-headed interferometer system which is placed in a fixed locationand which positions the production head or, as previously described, thepositioning head 2.

A specific embodiment of the present invention is shown in FIG. 2 wherethe positioning body consists of a robot 11 of the type described inSwedish patent application No. 8502327-3 mentioned in the introduction.Otherwise the positioning device and positioning method are identical tothose described above. The robot 11 shown in FIG. 2, with its robotpositioning head 12, in combination with the present inventionconstitutes a robot control system with high precision.

The robot 11, see FIG. 3, used as positioning body in FIG. 2 comprisesthree actuators 21 each of which is in the form of a piston 22 which isdisplaced in a cylinder 23. The piston 22 is displaced inside thecylinder 23 by conventional drive means, not shown, which may behydraulic or pneumatic or may consist of a screw and nut mechanism or ofhydraulic fluid. Each cylinder end is secured via a joint 24 in a fixedstand or frame 25. The joint 24, enabling the cylinder 23 and piston 22to oscillate in all directions in relation to the frame 25, is shownhere as a cardan joint but may consist of any suitable type of universaljoint. Each piston 22 is connected via a similar joint 26 to a robotpositioning head 27. The actuators 21 are arranged along the side edgesof an imagined triangular pyramid and, by displacing the pistons 22 inrespective cylinders 23, the robot positioning head 27 is set in thedesired location, since the effective length of the actuator 21unequivocally determines the location of the robot positioning head 27.The robot includes the above-mentioned positioning control unit 3 whichemits signals to the actuators 21 which cause the robot positioning headto move to the desired location.

An arm 28 consisting of a sleeve 210 and a shaft, not shown, journalledin the sleeve 210 extends symmetrically from the robot positioning head27 between the actuators 21. The sleeve 210 is rigidly joined to therobot positioning head 27 and comprises two bearings arranged one ateach end of the sleeve, the shaft being pivotably journalled therein. Auniversal joint 211 is secured to the frame 25 in an area situated alongthe symmetry axis of the imagined pyramid. The universal joint 211 has acentral opening, the cross section of which is somewhat larger than theouter diameter of the sleeve 210. The sleeve 210 extends through thecentral opening of the joint and can be displaced in axial direction inrelation to the frame 25 and joint 24, at the same time as it can be setat an optional angle in relation to the frame 25, the sleeve 210 thusbeing controlled radially and being secured against turning in the joint24. The sleeve 210 is sufficiently long for it always to be in thecentral opening of the universal joint 211 within the total range ofmovement of the robot positioning head 27.

The sleeve 210 is provided with a pivot motor, not shown, the turningmovements of which, via suitable transmission, provide the shaft withdesired turning movement.

The shaft end protruding out through the robot positioning head 27supports a suitable manipulation device which may consist of amotor-operated gripping device 29. The gripping movements of thegripping device may be controlled with the aid of operating rods runningaxially and rotatably inside the sleeve 210 and extending out over theother end of the sleeve 210 and connected to suitable operating means.

In FIG. 3 the arm 28 between the actuators 21 consists of a shaft andsleeve unit. However, it may also consist of only a shaft journalled inthe universal joint 211 and in the robot positioning head 27. The numberof actuators may be more than the three shown in the drawings. Nor dothey need to be symmetrically arranged around the arm 28. The shaft mayalso be arranged displaceable in the sleeve 210.

What is claimed is:
 1. A positioning device for a production system forpositioning the location of a positioning head in relation to a workobject, comprising: a positioning body, a positioning control unit forthe positioning body, a control data system for the positioning controlunit, a three-dimensional localisation measuring system arranged tocommunicate with the control data system and comprising at least onerecording device for determining and adjusting the location of thepositioning head in space, the recording device being arranged to recordand determine the spatial location of the positioning head in relationto the work object with target devices whose locations can be accuratelymeasured, arranged with respect to the work object and the positioninghead.
 2. A positioning device as claimed in claim 1, characterized inthat the recording device comprises an electro-optical recording device.3. A positioning device as claimed in claim 2, characterized in that therecording device comprises a multi-headed interferometer system.
 4. Apositioning device as claimed in claim 2, characterized in that one ormore electro-optical recording devices are arranged in the vicinity ofthe positioning body to enable the localisation measuring system torecord the location of the positioning body and the work object in spacethrough triangulation.
 5. A positioning device as claimed in claim 1,characterized in that an object identifier is connected to thepositioning control unit.
 6. A positioning device as claimed in claim 1,characterized in that the recording device is arranged to simultaneouslyrecord the location of the positioning head and of the work object inspace.
 7. A positioning device as claimed in claim 1, wherein the targetdevices are on the work object and the positioning head.
 8. Apositioning device as claimed in claim 1, wherein at least one of thetarget devices is on an object having a fixed and stable relationship tothe work object.
 9. A positioning device as claimed in claim 1, whereinat least one of the target devices is on an object having a knownrelationship to the positioning head.
 10. A positioning device asclaimed in claim 2, wherein the electro-optical recording device is a 3Dvision system.
 11. A positioning device as claimed in claim 2, whereinthe electro-optical recording device is a laser tracker.